Heat sealing apparatus



April 11, 1961 w. E. STAGEBERG HEAT SEALING APPARATUS Original FiledDec. 51, 1956 United States Patent HEAT SEALING APPARATUS Wilfred E.Stageberg, Terre Hante, Ind., assignor t Bemis Bro. Bag Company, St.Louis, Mo., a corpora tion of Missouri Continuation of application Ser.No. 631,827, Dec. 31, 1956. This application Jan. 11, 1960, Ser. No.1,820

7 Claims. (Cl. 154-42) Among the several objects of the invention may benoted the provision of apparatus for producing a strong and dependablecontinuous heat seal between the edges of two or more superimposedlayers of heat-scalable sheet material, such as polyethylene; and theprovision of apparatus of this class which is economical to build andeasy to set up and maintain. Other objects and features will be in partapparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

Fig. 1 is a plan view of an apparatus of this invention, showing twolayers of material being edge-sealed;

Fig. 2 is a side elevation of Fig. 1; and,

Figs. 3 and 4 are enlarged cross sections taken on lines 33 and 4-4 ofFig. l, with the layers shown as separated for purposes of illustration.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Referring to the drawings, an apparatus of this invention is shown tocomprise a slitter .1 for trimming otf'a portion of two or moresuperimposed layers of heatsealable sheet material, such aspolyethylene, and providing aligned fresh-cut edges for the layers withsome degree of mechanical adhesion between the layers at said edges. Asillustrated, the slitter 1 comprises a circular knife 3 and a hardenedsteel roll or mandrel 5. Two layers of material are shown, designated 7and 9. The apparatus further comprises means for drawing the layersthrough the slitter in a plane path extending from the slitter to thedrawing means. As shown, this drawing means comprises a pair of drawrolls 11. These are positively driven by any suitable means (not shown)to draw the layers through the slitter at a. predetermined speed.

The knife 3 of the slitter is located near one end of the roll 5 to himoff a narrow marginal portion of each layer as indicated at 13, thetrimmed-01f material being disposed of as waste. The cut made by theslitter is a crush cut, and results in mechanical adhesion of the layersalong the aligned fresh-cut edges of the layers as indicated at A inFig. 3; This adhesion or initial welding together of the layers ,by theslitting action is advantageous. It appears to facilitate fusion of theedges of the layers.

The apparatus further comprises means for eifecting heat-sealingtogether of the fresh-cut edges of the layers as they travel in thestated plane path from the slitter 1 to the draw rolls 11. As shown,this means comprises an electrical resistance heater bar 15 (such as aNichrome bar) 2,979,113 Patented Apr. 11, 1961 adapted to be heated byflow of suitable current therethrough to a temperature sufiicient toeffect melting of the heat-sealable material. Bar 15 is located betweenthe slitter and the draw rolls in the plane of the layers and, as shownin Fig. 1, it extends at an angle to the direction of travel of thelayers and is adapted to melt back the fresh-cut adhered edges of thelayers and form a fused bead therealong. The rearward end of the bartoward the slitter 1 is located outward of the plane 8-8 in which thelayers are slit by the slitter, and the bar is angled inward toward thelayers at an angle indicated at Y in Fig. 1 which corresponds to therate at which the layers are melted back by the bar. Sufiicient distanceZ is allowed between the bar and the draw rolls for cooling of thematerial before it contacts the draw rolls.

The above-describedarrangement is such that as the layers with theiraligned fresh-cut adhered edges pass alongside the bar 15 (heated to redheat in the case of polyethylene layers, for example), the radiant heatfrom the bar melts the edges of the layers back, creating a bead ofmolten material along the layers in the zone indicated at X in Fig. l.The angle Y at which the bar 15 is set in respect to the direction oftravel of the layers corresponds to the rate at which the layers aremelted back, and is related to the speed of the layers (the heavier theseal desired, the slower the speed of the layers and the greater theangle Y). The edges of the layers do not actually touch the bar. Theymelt back in such manner that the molten bead does not come into contactwith the bar. To the eye, the gap between the bar and the layers seemsto be an area of intense gaseous heat.- During the travel of thematerial through the distance Z, the bead cools and becomes a strongdependable seal, being indicated at B in Fig. 4.

The following example illustrates the invention. The

bar 15 was approximately eight inches long and was set at an angle ofapproximately one-eighth inch in eight inches of length. Two layers oftwo mil polyethylene were drawn through the apparatus at a speed ofapproximately one hundred feet per minute. Distance Z was approximatelyfive feet. The bar was heated to a very bright red. It will beunderstood that the invention is not limited to the use of an electricalresistance heater bar. Other heater means may be used, such as a gasburner producing a series of flames, or a bar which is heated (to redheat, for example) by a gas burner or other suitable means.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in'the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. Apparatus for heat-sealing two or more superimposed layers ofheat-scalable sheet material along aligned edges thereof comprising aheating means, and means for feeding two ore more such superimposedlayers of heat-scalable sheet material toward and past said heatingmeans with said layers traveling in a predetermined path and with saidaligned edges traveling in a predeterminedplane normal to said path tosaid heating means, said heating means comprising an elongate heaterangled inward in the direction toward the edges of the layers from itsrearward end toward its forward end and adapted to melt back said edgesand form a fused bead therealong without contacting said edges.

2. Apparatus for heat-sealing two; or more superimposed layers ofheat-scalable sheet material along aligned edges thereof comprising aslitter for trimming E a portion of two or more such superimposed layersof heat-scalable sheet material and providing aligned freshcut edges forthe layers with some degree of mechanical adhesion between the layers atsaid edges, means for drawing the layers through the slitter in apredetermined path extending from the slitter to said-drawing means, andmeans for effecting heat-sealingtogether of said fresh-cut edges as thelayers travel from theslitter to said drawing means, said fresh-cutedges traveling from said slitter to said heat-sealing means ,in theplane in which the layers are slit by the slitter, said heat-sealingmeans comprising an elongate heater and means supporting said heater ina fixed position] between the slitter and the drawing means extendingalongside theedges throughout a portion of said path with the rearwardend of the elongate heater toward the slitter located outward of butclosely adjacent to said plane in which the layers are slit by theslitter and with the heater angled inward in the direction toward theedges of the layers from its rearward end to its forward end and adaptedto melt back said edges and form a fused bead therealong withoutcontacting said edges.

3. Apparatus for heat-sealing two or more superimposed layers ofheat-sealable sheet material along aligned edges thereof comprising aslitter constituted by a circular knife and a mandrel for trimming ofi?a portion of two or more such superimposed layers of heat-scalable sheetmaterial by means of a crush cut and providing aligned fresh-cut edgesfor the layers with some degree of mechanical adhesion between thelayers at said edges, means for drawing the layers through the slitterin a plane path extending from the slitter to said drawing means,,andmeans for effecting heat-sealing together of said fresh-cut edges as thelayers travel from the slitter to said drawing means, said fresh-cutedges traveling from said slitter to said heat-sealing means in theplane of said circular knife, said heat-sealing means comprising anelongate heater and means supporting said heater in a fixed positionbetween the slitter and the drawing means extending alongside the edgesthroughout a portion of said plane path with the rearward end of theelongate heater toward the slitter located outward of but closelyadjacent the plane of the circular knife and with the heater angledinward in the direction toward the edges of the layers from its rearwardend to its forward end and adapted to melt back said edges and form afused bead therealong without contacting said edges.

4. Apparatus for heat-sealing two or more superimposed layers ofheat-scalable sheet material along aligned edges thereof comprising aslitter constituted by a circular knife and a mandrel for trimming otf aportion of two or more such superimposed layers of heat-scalable sheetmaterial by means of a crush cut and providing aligned fresh-cut edgesfor the layers with some degree of mechanical adhesion between thelayers at said edges, draw rolls for drawing the layers through theslitter in a plane path extending from the slitter to said draw rolls,and means for effecting heat-sealing together of said fresh-cut edges asthe layers travel from the slitter to said draw rolls, said fresh-cutedges traveling from said slitter to said heat-sealing means in theplane of said circular knife, said heat-sealing means comprising anelongate electrical resistance heater bar and means sup- 4 v portingsaid bar in a fixed position between the slitter and the draw rolls inthe plane ofsaid layers extending alongside the edges throughout aportion of said plane path with the rearward end of the bar toward theslitter located outward of but closely adjacent the plane of thecircular knife and with thebar angled inward in the direction toward theedges of the layers from its rearward end to its forward end and adaptedto melt back said edges and form a fused bead therealong withoutcontacting said edges, the distance from the bar to the draw rolls beingsufficient for cooling of the bead before contacting the draw rolls.

5. Apparatus for heat-sealing two or more superimposed layers ofheat-scalable sheet material along aligned edges thereof comprisingmeans for trimming off a portion of two or more such superimposed layersof heatsealable sheet material and providing aligned edges for thelayers, means for feeding the layers through and past said trimmingmeans with said layers traveling in a predetermined path, and means foreffecting heat-sealing together of said-aligned edges as the layerstravel beyond the trimming means, said aligned edges traveling from thetrimming means to the heat-sealing meansin the plane in which the layersare trimmed by the trimming means, said heat-sealing means comprising anelongate heater and means supporting said heater in a fixed positio'uwith one side of the heater in the plane of said layers and opposed tosaid edges and with'said heater extending closely adjacent to but notcontacting said edges, the rearward end of said heater being locatedoutward of the plane in which the layers are trimmed by the trimmingmeans and said heatcrextending forward in such direc tion in relation tothe edges of the layers that when heated it is adapted to melt back saidedges and form a fused bead therealong without contacting said edges.

6. Apparatus tor, heat-sealing two or more supernnposed layers ofheat-scalable sheet material along aligned edges thereof comprising acrush-cutslitter for trimming oil a portion of two or more suchsuperimposed layers of heat-scalable sheet material and providingaligned fresh-cut edges for the layers with some degree of mechanicaladhesion between the layers at said edges, means for feeding the layersthrough and past the slitter with said layers traveling in apredetermined path, and means for effectingheabsealing together of saidfresh-cut edges as the layers travel beyond the slitter, said fresh-cutedges traveling from the slitter to the heat-sealing means in the planein which the layers are slit by the slitter, said heat-sealing meanscomprising an elongate electrical resistance heating bar and meanssupporting said bar in a fixed position with one side of the bar in theplane of said layers and opposed to said edges and with said barextending closely adjacent to but not contacting said -edges, therearward end of said bar being located outward of the plane in which thelayers are slit by the slitter and said bar extending forward, in suchdirection in relation to the edges of the layers that when heated it isadapted to melt back said edges and form a fused bead therealong withoutcontacting said edges.

7. Apparatus as set forth in claim 6 wherein said slitter comprises acircular knife and a mandrel.

References Cited in the file of this patent UNITED STATES PATENTS2,556,476 Lamport June 12, 1951 2,711,779 Carland June 28, 19552,756,819 Judelson July 31, 1956 2,759,524 Davis Aug. 21, 1956

